Product Features
WD Scorpio ML160M
18
RELEASED 1/16/09 (WD CONFIDENTIAL)
2679-701205-A00
Defects managed at the factory are sector slipped. Grown defects that can occur in the field
are mapped out by relocation to spare sectors on the inner cylinders of the drive.
3.6.9
Automatic Defect Retirement
The automatic defect retirement feature automatically maps out defective sectors while
reading or writing. If a defective sector appears, the drive finds a spare sector.
The following item is specific to automatic defect retirement on writes (write auto-relocation):
Data is always written to disk (using automatic defect retirement if required) and no error
is reported.
The following item is specific to automatic defect retirement on reads (read auto-relocation):
When host retries are enabled, the drive will internally flag any unrecoverable errors
(DAMNF or ECC). This flagging allows subsequent write commands to this location to
relocate the sector only if the sector test fails.
3.6.10
Error Recovery Process
The drive has five means of error recovery:
ECC On-the-Fly
Read/Write Retry Procedure
Extended Read Retry Procedure
ECC On-the-Fly – If an ECC error occurs, the drive attempts to correct it on-the-fly without
retries. Data can be corrected in this manner without performance penalty. The details of the
correction algorithm appear in the next section.
Read/Write Retry Procedure – This retry procedure is used by all disk controller error types. If
the procedure succeeds in reading or writing the sector being tried, then recovery is complete
and the controller continues with the command. Each retry operation also checks for servo
errors. The procedure ends when error recovery is achieved or when all possible retries have
been attempted.
Extended Read Retry Procedure – This retry procedure tries combinations of positive/negative
track offsets and data DAC manipulations to recover the data. This retry procedure applies
only to read data recovery. The Read/Write Retry procedure performs the actual retry
operation.
When an extended retry operation is successful, the controller continues with the command.
The controller clears any changes in track offset or data DAC settings before the command
continues.
3.7
Fluid Dynamic Bearings (FDB)
Bearing design that incorporates a layer of high-viscosity lubricant instead of ball bearings in
the hard drive spindle motor. As an alternative to conventional ball bearing technology, FDB
designs provide increased non-operational shock resistance, speed control, and improved
acoustics.
3.8
CacheFlow™
CacheFlow is WD’s unique, multi-generation disk caching system. It incorporates read cache
with write cache.
WD designed CacheFlow to obtain maximum performance with today’s most popular
operating systems and applications. CacheFlow increases performance over prior caching
algorithms by increasing the number of times that requested data is in the cache. This reduces
